PVMBG reported that during 7 June-9 December white-to-gray plumes rose from Ibu’s craters. Observers in Goin (7 km NNW) noted that the lava dome, which had grown taller than the N crater rim in June, continued to grow; incandescent material from the dome filled the river valley in the direction of the Duono Village, about 5 km NW. Seismicity remained relatively stable. On 10 December the Alert Level was lowered to 2 (on a scale of 1-4). The public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.

In the first nine months of 2011, Ibu was the scene of frequent avalanches and at least one weak explosion that generated minor white-to-gray plumes (BGVN 36:08). Seismic activity decreased during September 2011, prompting the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to lower the Alert Level to 2 (on a scale of 1-4) on 8 September (the Level rose again later). This report discusses activity from 9 September 2011 through March 2014. The location of Ibu is shown in BGVN 36:08.

According to CVGHM, seismicity increased and volcanic tremor was detected during May through 6 June 2013. The lava dome grew, especially the N part, and by early June had grown taller than the N crater rim. White-to-gray plumes rose 200-450 m above the crater rim. Based on visual and instrumental observations, as well as the hazard potential, CVGHM increased the Alert Level to 3 on 7 June. The public was warned to stay at least 3 km away from the active crater.

CVGHM reported that during 7 June-9 December 2013, the lava dome continued to grow, and incandescent material from the dome filled the river valley in the direction of Duono village, about 5 km NW. The seismicity remained relatively stable. Observers saw occasional weak white-to-gray plumes. On 10 December 2013, the Alert Level was lowered to 2; however, the public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.

Between 1 September 2011 and March 2014, MODVOLC thermal alerts were issued on 70 days, or an average of almost one day every two weeks. Such alerts are consistent with dome growth such as that noted above. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.) For comparison, between 1 January 2011 and 13 September 2011, these alerts only appeared about once every 2.4 weeks on average.

Weekly Reports - Index

PVMBG reported that during 7 June-9 December white-to-gray plumes rose from Ibu’s craters. Observers in Goin (7 km NNW) noted that the lava dome, which had grown taller than the N crater rim in June, continued to grow; incandescent material from the dome filled the river valley in the direction of the Duono Village, about 5 km NW. Seismicity remained relatively stable. On 10 December the Alert Level was lowered to 2 (on a scale of 1-4). The public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.

CVGHM reported that during May through 6 June white-to-gray plumes rose 200-450 m above Ibu's crater rim. Seismicity increased and volcanic tremor was detected. The lava dome contained to grow, especially the N part, and in early June had grown taller than the N crater rim. Based on visual and instrumental observations, as well as the hazard potential, CVGHM increased the Alert Level to 3 (on a scale of 1-4) on 7 June. The public was warned to stay at least 3 km away from the active crater.

CVGHM reported mostly clear conditions at Ibu during January-8 September and that white-to-gray plumes were observed rising 200-400 m above the craters. On 20 August observers from the nearby villages of Goin and Duono noted multiple eruptions from the S, E, and N craters. Eruption "smoke" rose 50-250 m above the craters and an avalanche traveled 300 m. Seismicity indicating avalanches occurred on average 45 times per day during January-8 September. Other types of seismic signals fluctuated during the time period but stabilized or decreased towards September. Based on visual observations and seismicity, CVGHM lowered the Alert Level to 2 (on a scale of 1-4) on 8 September.

CVGHM reported that white and gray plumes from Ibu rose 300-400 m above the crater rim during 15 July-4 August, and that earthquakes became more frequent during 27 July-4 August. Lava flows were seen on 2 August. Later that day, a thunderous sound was followed by incandescence at the summit. On 3 August, incandescent material was ejected as high as 20 m above the crater. On 5 August, the Alert Level was increased to 3 (on a scale of 1-4). The growing lava dome had reached a height so that it was visible from Duono Village, about 5 km NW. Residents and tourists were not permitted within 2 km of the crater.

CVGHM reported that white and gray plumes from Ibu rose 600 m above the crater rim prior to 11 July and 400 m above the crater afterwards. Ashfall was reported in nearby areas, within a 3-km-radius of Ibu. Based on information from the Gamsungi observation post and seismic data, CVGHM lowered the Alert Level on 16 July from 3 to 2 (on a scale of 1-4). Residents and tourists were not permitted within 2 km of the crater.

CVGHM reported that seismicity from Ibu increased during 6-14 April and remained elevated during 15-20 April. Plumes described as "eruption smoke" rose to altitude of 1.8-2.1 km (5,900-6,900 ft) a.s.l. during 12-21 April and were gray during 18-21 April. The Alert Level was increased to 3 (on a scale of 1-4) on 21 April. Residents and tourists were not permitted within 2 km of the crater.

CVGHM reported that white plumes from Ibu rose to an altitude of 1.5 km (5,000 ft) a.s.l. during 17-31 March and were spotted "often." The plume altitudes increased to 1.6 km (5,200 ft) a.s.l. on 31 March. During 4-5 April, seismicity increased in amplitude and plume altitude increased to 1.8-2.0 km (5,900-6,600 ft) a.s.l. On 5 April, the eruption plume was gray and material fell onto the crater. The Alert Level remained at 2 (on a scale of 1-4). The community was not permitted to climb or approach the crater.

Information is preliminary and subject to change. All times are local (unless otherwise noted)

Ibu volcano on Halmahera island started erupting on 31 December 1998. A plume rose to 1,000 m above the summit as a result of mild explosions. On 2 January, personnel from the Volcanological Survey of Indonesia (VSI) who went to the island to take COSPEC measurements observed an eruption. Ashes were deposited to ~3 mm depth in surrounding villages. On 5 January another eruption lasted for 60 minutes. Local people reported that a lava flow reached the lower lip of the crater on 16 January.

Local residents first noticed thick gray ash emissions from the summit on 18 December 1998 (corrected from BGVN 24:01); this information reached the Volcanological Survey of Indonesia (VSI) Gamkonora volcano observatory on the 31st. On 2 January personnel from VSI who went to the island to take COSPEC measurements of the SO2 release observed a loud eruption that caused up to 3 mm of ashfall in and around Tugure Batu Village. The eruption lasted 35 minutes and generated a plume 1,000 m high. Another eruption observed on 5 January 1999 lasted for 60 minutes. Thunderclaps from the summit were heard on 16 January and a night glow from ejecta was evident above the summit area. Residents also reportedly saw lava at the crater rim. The seismometer from Gamkonora (an RTS PS-2) was installed ~2 km from the summit of Ibu on 3 February along with an ARGOS satellite system tiltmeter.

Field observations on 11 March revealed continuing eruptions and rumbling noises, but the larger eruptions (accompanied by booming and thick ash ejection) had decreased to a rate of one every 15-20 minutes. When observed on 2 February larger eruptions occurred every 5 minutes. Seismograph records are still dominated by explosion events; during 9-15 March there were 779 events, increased from 673 events the previous week.

"White ash emissions" were noted between 9 March and 24 May, rising as high as 700 m above the crater rim but more often 100-200 m. On 11 March it was noted that larger eruptions, accompanied by booming noises and thick ash emission, had decreased to every 10-15 minutes from every 5 minutes during the previous observations on 2 February. Signals from seismic events were dominated by those from the eruptive events, which occurred at a rate of over 100 per day in March and reduced to half that number in April and May.

The last reported activity at Ibu included ash emission and mild ash explosions in September 1999. A May 2000 photo showed a lava dome covering the crater floor. MODIS data after May 2000 indicated thermal alerts during 28 May-3 October 2001 (figure 1). The series of alerts was consistent with continued inflation of, or extrusion onto, this dome. Note that the alert was barely above threshold, and it is likely that Ibu was just below detection threshold through 2002. A discussion of the MODIS technique was included in BGVN 28:01.

The Directorate of Volcanology and Geological Hazard Mitigation (DVGHM) released ten nearly identical weekly reports on Ibu during 31 May-29 August 2004. They noted that Ibu emitted "white ash" (steam plumes) reaching ~ 50-150 m above the crater rim. Continued growth of the intracrater lava dome was either recognized or assumed. Ibu lacked a working seismic instrument. Its hazard status remained at Level II (Yellow, a condition meaning 'caution or on guard' ('waspada' in Indonesian).

During late March through late April 2008, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) described mainly white plumes emitted from Ibu. On at least five days, however, the plumes were gray. During 17-31 March, frequent white plumes rose to an altitude of 1.5 km. On 31 March the plume altitudes increased to 1.6 km.

During 4-5 April 2008, seismicity increased in amplitude and plume altitude increased to 1.8-2.0 km. On 5 April, the eruption plume was gray and material fell around the crater. Residents of nearby communities were not permitted to climb or approach the crater.

Plumes that were possibly gray rose to altitudes between 1.6 and 1.9 km during 6-17 April. Gray plumes rose to altitudes of 2-2.1 km during 18-21 April. On 21 April, CVGHM warned that residents and tourists were not permitted within 2 km of the crater.

Steam plumes rose above the crater during late May to late August 2004 (BGVN 30:03). Thermal anomalies detected by the MODIS instruments triggered MODVOLC thermal alerts (table 1) during that interval and the last quarter of 2004; alerts were also noted during February 2005, but not in 2006 and 2007. Thermal anomalies were again measured by the MODIS instrument in mid-May 2008 and continued to be detected through late October.

Table 1. MODVOLC thermal anomalies over Ibu from late August 2004 to 20 October 2008. Courtesy of the HIGP Thermal Alerts System.

Our last report on Ibu summarized MODVOLC thermal alerts (satellite thermal anomalies) from mid-May through late October 2008 (BGVN 33:09); those anomalies continued to be recorded almost monthly through June 2009. The anomalies suggest continued growth of a lava dome in the crater, an event previously documented by a photograph taken May 2000 and mentioned in BGVN 28:03. Authorities raised the hazard alert to Level 3 during June 2008. Several photos of Ibu in 2007 were taken by Arnold Binas (figure 2).

Figure 2. Photos of Ibu taken on 27 July 2007 from a point on the NW crater rim, looking approximately SE. The top photo shows the location of the dome in the steep-walled crater. The bottom photo shows a close-up view of the dome. Courtesy of Arnold Binas.

Thermal anomalies detected by satellites (MODVOLC thermal alerts) through June 2009 suggested continued growth of a lava dome in the crater (BGVN 34:05). The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that prior to 11 July 2009, white and gray plumes from Ibu rose ~ 600 m above the crater rim. After 11 July, the plumes were gray and rose only ~ 400 m above the crater rim. Ash from the gray plumes fell on areas within a 3-km radius of Ibu.

Observers noted an increase of eruptive activity after mid-July. During the period 27 July to 3 August, the total number of eruptive events showed a tendency to increase. Each eruptive earthquake was then followed by the expulsion of lava that reached the upper slopes. Plumes seen during 15 July to 4 August 2009 were grayish-white and reached a height of ~ 300-400 m above the crater rim. The lava extrusions accompanied rather strong rumbling noises on five occasions. The incandescent material was seen coming from the summit on 2 August 2009, and lava flows were seen. Later that day, a thunderous sound was followed by incandescence at the summit.

On 3 August, incandescent material was ejected as high as 20 m above the crater. The total of explosion earthquakes increased from the 20-49 events of mid-July to 50-80 events during 27 July to 4 August. Villagers in Desa Duono, Going, and Sanghaji noted strong rumbling sounds. No volcanic earthquakes were recorded during that time frame. On 4 August 2009, 82 volcanic earthquakes were recorded. Each eruptive earthquake was followed by the expulsion of lava which reached the upper slopes.

The observation post in the village of Duono, 5 km NW of Ibu, reported that the lava dome continued to grow. As a result, local residents were advised to prepare for times when they needed to wear masks that cover both the nose and the mouth. Visitors and tourists were asked to remain at least 2 km from the crater.

Activity at Ibu (figure 3) has been frequent since December 1998; the current eruption began in April 2008. Thermal alerts (MODIS/MODVOLC) continued into June 2009, and incandescent ejections were seen in early August (BGVN 34:10).

Between July 2009 and June 2010, thermal alerts at Ibu were detected by MODVOLC on an average of about five or more days every month (normally one pixel per pass?at least one alert each 55 days during the 1-year period), about the same frequency as those measured during the first half of 2009 and far more frequent than that for the 4-year period October 2004-October 2008 (BGVN 33:09). Ground observations reported below in August-September 2009 and January 2010 confirm continued doem growth.

The Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that white and gray plumes rose 300-400 m above the crater rim during 15 July-4 August 2009 and that earthquakes became more frequent during 27 July-4 August 2009. Lava flows were seen on 2 August. Later that day, a thunderous sound was followed by incandescence at the summit. On 3 August, incandescent material was ejected about 20 m above the crater. The lava dome had reached a height sufficient to be seen from Duono Village, about 5 km NW.

Mark Rietze and Alain de Toffoli took some photographs of Ibu during a 31 August-7 September 2009 visit (figures 4-7), posted on the website of Th. Boeckel. The travelers noted that during the last 10 years the crater has been filled with a lava dome. The volcano has several vents that discharge ash and gas, along with Strombolian ejections. Only two vents were active during the visit.

Figure 4. Photo of the edge of the Ibu crater, taken during 25 August-8 September 2009. The vegetation near the rim was partially charred, and lava from the dome caused small bush fires. Photo taken from the W rim looking toward the E rim. Courtesy of Alain de Toffoli and M. Rietze.

Figure 5. Gas and ash emissions from the growing dome at Ibu, taken during 25 August-8 September 2009. Photo taken from the W rim looking E. Courtesy of Alain de Toffoli and M. Rietze.

Figure 6. Two active vents in Ibu's crater, taken during 25 August-8 September 2009. Photo taken from the W rim looking E. Courtesy of Alain de Toffoli and M. Rietze.

Figure 7. Dome growth in Ibu's crater with Strombolian ejections, taken during 25 August-8 September 2009. Photo taken from the W rim looking E. Courtesy of Alain de Toffoli and M. Rietze.

Arnold Binas posted some photos that demonstrated rapid dome growth (figure 8). Before 1998, the crater was vegetated down to the bottom. The dome was distinctly lower in 2007 (BGVN 34:05). Binas commented that "After a period of no steam emissions at all, [the dome vent] would start steaming slightly to announce it's next eruption. After being done emitting rocks and ash, it would steam vigorously for a while before quieting down again." Binas was also told that material had started to go through a breach in the N side of the crater.

Figure 8. Growth in a single day at Ibu's dome from one of the two vents erupting around 21 January 2010. The top photo was taken during a moment of quiet, and is the older image. Both photos taken from the W rim looking E. Courtesy of Arnold Binas.

A recent article by Agustan and others (2010) used radar to measure ground deformation related to volcanic activity on Ibu. Specifically, they used longer wavelength (L-band) differential interferometry to identify an inflation-deflation region, especially in the crater area before the March-April 2008 eruption (BGVN 33:09).

Ibu (figure 9) has been intermittently active since 1998. Small explosions were noted during 2009 through January 2010 (BGVN 35:05). This report discuss seismic events from January 2011 to September 2011.

According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), during January 2011 to 8 September 2011, white-to-gray plumes rose 200-400 m above the craters. For 2011, CVGHM reported seismically detected avalanches, which on average occurred 45 times/day during January-April, 60 times/day during May-July, and 46 times/day during the first week of September. During much of 2011 seismicity fluctuated, but decreased towards September, prompting CVGHM to lower the Alert Level to 2 (on a scale of 1-4) on 8 September.

During 2010, MODVOLC thermal alerts appeared about once per week on average, whereas, during 1 January 2011 through 13 September 2011, these alerts only appeared about once every 2.4 weeks on average. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.)

In the first nine months of 2011, Ibu was the scene of frequent avalanches and at least one weak explosion that generated minor white-to-gray plumes (BGVN 36:08). Seismic activity decreased during September 2011, prompting the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to lower the Alert Level to 2 (on a scale of 1-4) on 8 September (the Level rose again later). This report discusses activity from 9 September 2011 through March 2014. The location of Ibu is shown in BGVN 36:08.

According to CVGHM, seismicity increased and volcanic tremor was detected during May through 6 June 2013. The lava dome grew, especially the N part, and by early June had grown taller than the N crater rim. White-to-gray plumes rose 200-450 m above the crater rim. Based on visual and instrumental observations, as well as the hazard potential, CVGHM increased the Alert Level to 3 on 7 June. The public was warned to stay at least 3 km away from the active crater.

CVGHM reported that during 7 June-9 December 2013, the lava dome continued to grow, and incandescent material from the dome filled the river valley in the direction of Duono village, about 5 km NW. The seismicity remained relatively stable. Observers saw occasional weak white-to-gray plumes. On 10 December 2013, the Alert Level was lowered to 2; however, the public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.

Between 1 September 2011 and March 2014, MODVOLC thermal alerts were issued on 70 days, or an average of almost one day every two weeks. Such alerts are consistent with dome growth such as that noted above. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.) For comparison, between 1 January 2011 and 13 September 2011, these alerts only appeared about once every 2.4 weeks on average.

Volcano Types

Tectonic Setting

Rock Types

Major
Andesite / Basaltic Andesite
Basalt / Picro-Basalt

Population

Within 5 kmWithin 10 kmWithin 30 kmWithin 100 km

1,560
14,549
64,581
637,988

Geological Summary

The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Synonyms

Iboe | Tobaru | Tubaru | Toebaroe

Craters

Feature Name

Feature Type

Elevation

Latitude

Longitude

Bitjara, Lake

Maar

Gam Itji, Lake

Maar

Mati, Lake

Maar

Moro

Crater

Todoke, Lake

Maar

Toduoko, Lake

Maar

Photo Gallery

Gunung Ibu volcano on the NW coast of Halmahera Island rises beyond a small village on its WNW flank. The summit of the stratovolcano is truncated by nested craters; the inner crater, 1 km wide and 400 m deep, contains several small crater lakes. The outer crater is breached on the north side, forming the deep valley seen here on the left side of the summit ridge. Few eruptions are known in historical time from Ibu, although it was erupting at the time of this February 1999 photo.

Photo by Agus Karim, 1999 (Volcanological Survey of Indonesia).

References

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.

EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).